1. Field of the Invention
The present invention relates to an electrical rotating machine.
2. Description of the Related Art
A permanent magnet embedded type electrical rotating machine having a rotor core provided with an embedded permanent magnet has been known in the related art. In addition, as a method to reduce cogging torque and torque ripple of the electrical rotating machine, a magnetic pole of a rotor or a stator has been arranged with inclination with respect to an axial direction, in the related art. A so-called skew structure is generally known.
A permanent magnet embedded type electrical rotating machine having a skew structure in the related art has been disclosed in Japanese Unexamined Patent Application Publication No. 2000-308287, for example. In a motor disclosed in Japanese Unexamined Patent Application Publication No. 2000-308287, a plurality of rotor core blocks provided with embedded permanent magnets are integrally formed in an axial direction while being deviated from each other in a rotation direction of a rotor (see claim 1 and Paragraph[0014] of Japanese Unexamined Patent Application Publication No. 2000-308287).
In the motor disclosed in Japanese Unexamined Patent Application Publication No. 2000-308287, an N-pole embedded in an rotor core block on an upper side and an S-pole embedded in an rotor core block on a lower side overlap each other in the rotational-axial direction, in two rotor core blocks adjacent to each other in the axial direction (see FIG. 1 and Paragraph[0015] of Japanese Unexamined Patent Application Publication No. 2000-308287). Therefore, magnetic flux leaving the N-pole on the upper side enters the S-pole on the lower side. The magnetic flux forms a short circuit loop inside the rotor, without being cross-linked with a stator outside the rotor. Therefore, torque is reduced (see Paragraph[0009] of Japanese Unexamined Patent Application Publication No. 2000-308287). That is, effectual magnetic flux of the rotor is reduced. In the motor according to the publication, a non-magnetic substance having a thin plate shape is interposed between the rotor core blocks, in order to suppress magnetic flux flowing from the N-pole on the upper side to the S-pole on the lower side (see Paragraph[0015] of Japanese Unexamined Patent Application Publication No. 2000-308287). However, if the N-pole on the upper side and the S-pole on the lower side overlap each other in the rotational axial direction, as in the motor according to the publication, it is difficult to further suppress the reduction in the effectual magnetic flux.